Multilayer coatings for use over surfaces of automobiles and trucks are well known in the art. Initially such compositions were organic solvent based. However, as environmental regulations became more prevalent, waterborne systems and high solids organic solvent-based systems have increased in popularity. However, such coatings typically require heating to achieve the desired physical and chemical properties. This has presented particular problems in the automotive refinish market where curing ovens are not used, and coatings for automotive refinish applications must attain the necessary physical and chemical properties at ambient temperature. In copending application Ser. No. 11/840,292, filed even date herewith, there is disclosed a radiation curable clearcoat composition based on a polyene and a polythiol. Such compositions can be formulated as high solids compositions and can be used over organic solvent-based and waterborne basecoats. Unfortunately, performance over waterborne basecoats is often less than desired. It is believed the coating derived from the waterborne basecoat contains residual moisture that adversely affects the humidity resistance of the multilayer coating.